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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Vol. 38 (1990), No. 1. (March), Pages 177-177

C.S.P.G. 1990 Convention, "Basin Perspectives"

Lower Devonian Reefs, Disappointment Bay Formation, Arctic Islands [Abstract]

Prosh, E.C.1

ABSTRACT

The Disappointment Bay Formation (Emsian) on Lowther Island, Northwest Territories, consists of an 85 to 90 m thick sequence of upward-shoaling limestones and dolomites. Within the upper two thirds of the formation, exhumed reef mounds, about 50 m thick, are exposed. Four principal, vertically-successive reef facies can be distinguished: a basal stromatactis mudstone-wackestone; an algally-bound wackestone; a stromatoporoid-coral framestone; and a capping, crinoidal grainstone. Reef growth occurred in response to passive sedimentary shoaling, with the reefs nucleating upon small mounds of aggregated brachiopods. Following deposition of a thin stromatactis-mudstone, a thick sequence of dominantly algally-bound wackestone accumulated on the reefs. Ubiquitous, horizontally-disposed, large fibrous calcite cements within this wackestone can be shown to be early replacement products after algal crusts, on the bases of overgrowth relationships, fossil inclusions, cathodoluminoscopy, algal and other criteria. Steeply dipping, reef-flank debris beds also accumulated at this time, and show evidence of over-steepening through synsedimentary fissuring. With the transgression of mean wave-base, reef deposition changed dramatically to a stromatoporoid-coral framestone. Thin, capping, crinoidal grainstones indicate reefal senescence at the end of Disappointment Bay deposition. Partially penetrative dolomitization, affecting only the uppermost reef facies and margins, occurred under shallow burial conditions.

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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES

1 University of Western Ontario, London N6A 5B7

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